31081021 has 2 divisors, whose sum is σ = 31081022. Its totient is φ = 31081020.

The previous prime is 31081019. The next prime is 31081097. The reversal of 31081021 is 12018013.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18020025 + 13060996 = 4245^2 + 3614^2 .

It is a cyclic number.

It is not a de Polignac number, because 31081021 - 2¹ = 31081019 is a prime.

Together with 31081019, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 31080986 and 31081004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31082021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15540510 + 15540511.

It is an arithmetic number, because the mean of its divisors is an integer number (15540511).

Almost surely, 2^31081021 is an apocalyptic number.

It is an amenable number.

31081021 is a deficient number, since it is larger than the sum of its proper divisors (1).

31081021 is an equidigital number, since it uses as much as digits as its factorization.

31081021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48, while the sum is 16.

The square root of 31081021 is about 5575.0355155819. The cubic root of 31081021 is about 314.4115022165.

Adding to 31081021 its reverse (12018013), we get a palindrome (43099034).

The spelling of 31081021 in words is "thirty-one million, eighty-one thousand, twenty-one".